Various powders are used as powders for cosmetics such as makeup cosmetics, sunscreen cosmetics, mascara, nail enamel, and lipstick. There have been many investigations of surface treatment conducted with the aim of providing water repellency and oil repellency for different purposes. Such purposes include preventing makeup from wearing off due to sweat, tears, rain, outdoor sports, and swimming in the sea, and preventing color transfer to clothes, drinking vessels, and the like. Examples of methods that have been proposed include a method using a silica-coated powder, a method using a powder subjected to surface treatment with various silicone derivatives, and a method using a powder with water repellency and oil repellency, which is prepared by surface treatment with a surface treatment agent having a perfluoro group.
Regarding powder subjected to surface treatment with a surface treatment agent having a perfluoroalkyl group, a method that involves treatment with perfluoroalkylphosphate is known (patent document 1). However, powders treated with perfluoroalkylphosphate are difficult to apply properly, powdery, and adhere poorly to skin. For such reasons, a method using a powder treated with a combination of perfluoroalkylphosphate and another surface treatment agent has been proposed (patent document 2). However, a specific perfluoroalkyl group presents safety concerns. Hence, a surface treatment agent for powder has been required as an alternative to a surface treatment agent having such specific perfluoroalkyl group.
A surface treatment agent having a perfluoropolyether chain has been examined as a means to address the problem. As powders treated with a surface treatment agent having a perfluoropolyether chain, a powder treated with perfluoropolyetherphosphate ester and cosmetics comprising the same have been reported (patent documents 3 and 4). As a powder treated with a silane compound having a perfluoropolyether chain, a powder treated with a perfluoropolyether-modified amino silane compound has been reported (patent document 5). An anionic polymer containing perfluoropolyether has further been reported (patent document 6). However, these powders using such surface treatment agents are insufficient in terms of water repellency, oil repellency, and the like, and are also not satisfactory in terms of adhesiveness or texture. Also, a surface-treated powder produced with a surface treatment agent that enables simple and inexpensive forms of surface treatment has also been desired.    Patent document 1 JP Patent Publication (Kokai) No. 7-112915 A (1995)    Patent document 2 JP Patent Publication (Kokai) No. 2009-269866 A    Patent document 3 JP Patent Publication (Kokai) No. 2000-128737 A    Patent document 4 JP Patent Publication (Kokai) No. 2000-309509 A    Patent document 5 JP Patent Publication (Kokai) No. 2008-214229 A    Patent document 6 JP Patent Publication (Kokai) No. 2010-121099 A